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The Single UNIX &reg; Specification, Version 2<br>
Copyright &copy; 1997 The Open Group

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<h4><a name = "tag_000_005_599">&nbsp;</a>NAME</h4><blockquote>
getlogin, getlogin_r - get login name
</blockquote><h4><a name = "tag_000_005_600">&nbsp;</a>SYNOPSIS</h4><blockquote>
<pre><code>

#include &lt;<a href="unistd.h.html">unistd.h</a>&gt;

char *getlogin(void);
int getlogin_r(char *<i>name</i>, size_t <i>namesize</i>);
</code>
</pre>
</blockquote><h4><a name = "tag_000_005_601">&nbsp;</a>DESCRIPTION</h4><blockquote>
The
<i>getlogin()</i>
function returns a pointer to
a string giving a user name associated with the calling process,
which is the login name associated with the calling process.
If
<i>getlogin()</i>
returns a non-null pointer, then that pointer
points to the name that the
user logged in under, even if there are several login names with the
same user ID.
<p>
The
<i>getlogin()</i>
interface need not be reentrant.
<p>
The
<i>getlogin_r()</i>
function puts the name associated by the login activity
with the control terminal of the current process
in the character array pointed to by
<i>name</i>.
The array is
<i>namesize</i>
characters long
and should have space for the name and the terminating null character.
The maximum size of the login name is {LOGIN_NAME_MAX}.
<p>
If
<i>getlogin_r()</i>
is successful,
<i>name</i>
points to the name the user used at login,
even if there are several login names with the same user ID.
</blockquote><h4><a name = "tag_000_005_602">&nbsp;</a>RETURN VALUE</h4><blockquote>
Upon successful completion,
<i>getlogin()</i>
returns a pointer to the login name or a null pointer if the user's login name
cannot be found.  Otherwise it returns a null pointer
and sets
<i>errno</i>
to indicate the error.
<p>
The return value may point to static data
whose content is overwritten by each call.
<p>
If successful, the
<i>getlogin_r()</i>
function returns zero.
Otherwise, an error number is returned to indicate the error.
</blockquote><h4><a name = "tag_000_005_603">&nbsp;</a>ERRORS</h4><blockquote>
The
<i>getlogin()</i>
function may fail if:
<dl compact>

<dt>[EMFILE]<dd>
{OPEN_MAX} file descriptors are currently open in the calling process.

<dt>[ENFILE]<dd>
The maximum allowable number of files is currently open in the
system.

<dt>[ENXIO]<dd>
The calling process has no controlling terminal.

</dl>
<p>
The 
<i>getlogin_r()</i>
function may fail if:
<dl compact>

<dt>[ERANGE]<dd>
The value of
<i>namesize</i>
is smaller than the length of the string
to be returned including the terminating null character.

</dl>
</blockquote><h4><a name = "tag_000_005_604">&nbsp;</a>EXAMPLES</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_005_605">&nbsp;</a>APPLICATION USAGE</h4><blockquote>
Three names associated with the current process can be determined:
<i>getpwuid</i>(<i>geteuid</i>())
returns the name associated with the effective user ID of the process;
<i>getlogin()</i>
returns the name associated with the current login activity; and
<i>getpwuid</i>(.Fn<i>getuid</i>)
returns the name associated with the real user ID of the process.
</blockquote><h4><a name = "tag_000_005_606">&nbsp;</a>FUTURE DIRECTIONS</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_005_607">&nbsp;</a>SEE ALSO</h4><blockquote>
<i><a href="getpwnam.html">getpwnam()</a></i>,
<i><a href="getpwuid.html">getpwuid()</a></i>,
<i><a href="geteuid.html">geteuid()</a></i>,
<i><a href="getuid.html">getuid()</a></i>,
<i><a href="limits.h.html">&lt;limits.h&gt;</a></i>,
<i><a href="unistd.h.html">&lt;unistd.h&gt;</a></i>.
</blockquote><h4>DERIVATION</h4><blockquote>
<i>getlogin()</i> derived from System V Release 2.0.
<P>
<i>getlogin_r()</i> derived from the POSIX Threads Extension (1003.1c-1995).
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UNIX &reg; is a registered Trademark of The Open Group.<br>
Copyright &copy; 1997 The Open Group
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